Thermal over-current circuit-breaker



' Oct'; 16, 1956 .1. ELLENBERGr-:R 2,767,281

THERMAL OVER-CURRENT CIRCUIT-BREAKER Filed April 23,v 1951 2 ShetS-Sheet 1 B/ME T41.

.wezaol ef, ELI/ez?, 6123er gfonz'eya Oct. 16, 1956 J. ELLENBERGER 2,767,281

THERMAL OVER-CURRENT CIRCUIT-BREAKER Filed April 25, 1951 2 Sheets-Sheet 2 l i AI mm* 4* 11's United States Patent O M TI-ERMAL VER-CURRENT ClRCUIT-BREAKER Jakob Ellenberger, Altdorf, near Nrnberg, Germany,

assigner to Ellenberger & Poensgen G. n1. b. H., Altdor, near Numberg, Germany Application April 23, 1951, Serial No. 222,473

Claims priority, application Germany May 10, 1950 7 Claims. (Cl. 200-116)` Various forms of construction of thermal over-current circuit-breakers are already known and have been introduced to a large extent in practice in order to break an electric circuit at a predetermined maximum strength of current. Such an over-current circuit-breaker is known in which a small `amount of easily fusible metal in ia solid state holds firmly a guiding member cast into the metal which, when the metal fuses owing to the admissible current being exceeded, is released and under the action of a release spring effects the movement of the current carrying parts required for the interruption of the current.

Thermal over-current circuit-breakers have also been proposed in which a contact bridge, which is under the control of a spring, is held firmly in the switched-on position by a bi-metal spring which bends under the action of electric heating by the current to be controlled and when a critical current strength is reached releases the contact bridge and opens the circuit.

The invention relates to a thermal over-current circuitbreaker, suitable for the breaking of currents of from 0.2 to 40 arnperes, the construction of which is very simple as is also the arrangement of its individual parts, so that this over-current circuit-breaker can be made of small dimensions and of very flat shape.

An essential feature of the present invention is that the bi-metal spring is provided with an electric contact which feo-operates with 1a counter-contact provided on the contact bridge, by which counter-contact the current is closed over the two contacts in the switched-n position of the circuit breaker and is interrupted by the disconnection between -these contacts. The contact may be provided in any suitable position on the bi-metal strip. Preferably it is provided at the free end of a bi-metal spring, kept fixed on one side, the heating of which may be effected directly by the current ilowing through, as also indirectly by -a heating element adjacent to the bimetal strip, The contact on the bi-metal spring may, for instance, be made of copper and rest with a projection against a contact disc secured to the contact bridge in snch a manner that in the switched-on position the closure of the current between contact and counter-contact is self-locking. When the bi-metal strip bends owing to its being heated, the projection of the contact member secured to the bi-metal strip slides away from the contact plate, thereby releasing the movement of the contact bridge under the action of the spring. This movement, however, is connected with the interruption of the current which, according to the invention, flows through the two contacts.

According to the invention, the guiding `of the contact bridge is effected in a very simple manner in that a guiding rod is provided on the Contact bridge in its direction of movement, which rod is -displaceably mounted, for instance, in the opening of the transverse part of a metal frame. ln order to prevent tilting a lateral projection is provided in addition on the contact bridge, which projection is guided in a rail; also this rail may be secured 2,767,281 Patented Oct. 16, 1956 in the metal frame, which is closed underneath by :an insulating member.

In order to complete the circuit which flows from the bi-metal strip over the contact secured to its end to the contact disc, a contact stirrup is provided on the lower surface of the Contact bridge consisting of an insulating material, which stirrup is Iin electrically conducting connection with the contact disc and in the switched-on position engages in contact springs provided on an insulating member and connected with the output terminal of the circuit. In such an arrangement, when the bi-metal spring is bent not only is the self-locking contact on the contact disc interrupted but `also the contact stirrup is drawn out of the contact spring so that a current interruption takes place :also at this point. This arrangement has the advantage that solid contacts are provided for the current leads, which contacts .are disposed in an insulating member and do not partake of the movement of the contact bridge. Naturally, in the case of very simple constructions of circuit-breakers the second current interruption can be dispensed with, in which case the current connection to the movable contact disc must be effected in a diierent manner.

The over-current circuit-breaker may, according to a further feature of the invention, be provided with a switching off button, known per se. This may be eifected in a very simple manner, the bi-metal strip being provided rat its free end, preferably directly over the selflocking contact, with an angular bend against which abuts the guiding rod of the switching off button. it -has been found especially suitable in this case to provide the guiding rod at its other end with a spherical sliding piece. This arrangement allows of a very simple adjustment of the bent part of the bi-metal spring relatively to the sliding member, since the same exerts its action at each point of the bent part of the bi-metal strip reliably and results in a switching-oit device which can be operated reliably and very easily.

An especially simple form of construction of the overcurrent circuit-breaker hereinbefore described is obtained if use is made of :an insulating supporting member preferably arranged transversely to the metal frame referred to, on which the bi-metal strip as well as the metal stirrup, the guiding rail for guiding the contact bridge and the contact springs are secured next to one another.

With such an arrangement, the circuit-breaker can be manufactured so as to be very flat, since also the contact bridge and the other switch components can be easily manufactured in a ilat form.

According to the invention a heating element may be provided over the bi-metal strip, which is traversed by the current to be limited either in shunt with the bi-metal strip or alone or, as it may be desirable in the case of special applications, by a current of adjustable strength. The advantage of such an arrangement consists in that by varying the current strength in the auxiliary heating circuit, the switching-olf current strength of the circuitbreaker can be adjusted as desired.

The contact springs for the contact with the stirrup provided on the contact bridge need not be so disposed that the contact stirrup engages between the springs; in a modified form of the invention, only an angularly bent spring may be provided on the insulating supporting part, on which spring the contact stirrup rests with a likewise angularly bent end so that the said bent parts of the contact spring and stirrup touch each other in parallel at surfaces. This arrangement has the advantage that the contact spring, if constructed as a bi-metal strip, increases its pressure against the contact stirrup with increasing strength of current, thereby pressing also against the contact bridge, the contact disc of which comes in an especially intimate contact with the contact piece of the bi-metal strip until the bending of the bi-metal strip effecting the release releases the contact bridge. Thus, in this form of construction, a contact at the points of interruption which is improved by mechanical pressure is produced as the current rises until it is interrupted.

The Contact bridge need not be so constructed as to be provided with a guiding rod on one side and so that it runs with a lateral projection in a rail; it may also be provided with guiding rods on both sides or lie on a traversing guiding rod which is guided on two transverse limiting surfaces in openings providedV therein. In this case the release spring may be provided also in the lower part of the circuit-breaker and theV contact bridge be substanti'ally limited to a disc provided on the guiding rod, over which disc engages the projecting contact piece of the bi-metal spring. Underneath the contact bridge an insulatingy sleeve may be provided surrounding the guiding rod all round.VY

Such an arrangement has the advantage that after the current has been switched off, when the 1oi-metal strip returns to its. original position, an undesirable re-establishment of the current by contact between the contact piece of the bi-metal strip and the guiding rod, which in this case serves for the conduction of the current, cannot take place. The contact piece of the bi-metal strip approaching the guiding rod then remains separated from the guiding rod by the insulating sleeve until the current is switched on again by the actuation of the pressure button and therewith the descent of the contact bridge. The over-current circuit-breaker hereinbefore described is absolutely reliable, since the individual components of the circuit-breaker are of very simple construction. Each one of the components can be manufactured of small dimensions and it is easy to obtain a very dat construction of the circuit-breaker without the reliability thereof being in the least affected since the release by the direct action of the `contact bridge through the oi-metal strip results in ay very high uniformity in the switch-off value of current, without the intermediary of transmission elements. Finally, such a circuit-breaker can be manufactured very cheaply since the individual components are of very simple construction and the assembly does not cause any ditliculties.

The over-current circuit-'breaker according to the invention is suitable for different applications and more especially as an over-current safety device in electric installations of motor vehicles. Vln this case the circuitbreaker according to the invention is provided with metal plug pins by means of which they canl be plugged in on a base plate provided with metal sleeves next to one another, the munber of which depends upon the number of the circuits which are provided on the vehicle.

According to a further feature of the invention the plug pins are secured to metal strips' which are rmly attached to the insulating support member of the circuit-breaker carrying the bi-metal strip and the spring contact, preferably by screwing into the means sunk in the supporting member. One ofthe contact pins is in conducting connection with the bi-metal strip and the other one with the spring contact of the circuit-breaker so that the circuit is closed in the circuit-breaker through the two contact pins.

According tothe invention the sleeves are so arranged in a molded insulating plate, usualY in the electrical industry, that a number of circuit-breakers can be plugged in next to one another on the base' plate. The sleeves may be secured in the base plate, for instance by molding or pressing them in.

Metal strips may be attached to the sleevesV which are screwed on to the base plate and `carry the connecting terminals forl the leads on the side of the base plate Y facing the' circuit-breaker. Y

In. order better to insulate the individual: current carryingf partsl of the circuit-breaker according to vtheiizlvention,

casings of insulating material are provided which closely surround the circuit-breaker with the exception of the side provided with the contact pins. These casings preferably consist of molded material and can therefore be manufactured cheaply to exact dimensions. Each casing is connected with two small side cases for the protection of the contact terminals which are provided on the base plate, which side cases cover the contact terminals except for the open sides for the introduction of the leads, so that these current carrying parts are preferably insulated from one another.

The device according to the invention is naturally not limited to its application to motor vehicles and such an over-current switch board can be used anywhere where a quick and convenient exchange of circuit-breakers is desirable and where it is desired to instali an over-current circuit-breaker at a very small cost.

Owing to their simple construction the circuit-breakers operate reliably and without any disturbance andA avoid the replacement of fuses in the case of short-circuits. After the release and switching oit and after removal of the short circuit the only thing that is required is to press down the switch-on button of the over-current circuitbreaker in order to render the installation again ready for operation.

The over-current circuit-breaker according to the invention is illustrated by way of example in the accompanying drawings. Figures l to 9 show one form of construction with a double spring Contact; Figures 10 and 1l show a modification with bent single spring contacts and Figures 12 and 13 show a modilcation of the construction of the guide for the contact bridge. Figure 14 shows a form of construction of the circuit-breaker, especially suitable for motor vehicles.

Referring to the drawings,

Figure l is a sectional elevation of the over-current circuit-breaker;

Figure 2 is a view from below of Figure l;

Figure 3 is a section along the line Ill-lll of Figure l;

Figure 4 is a section along the line lV-IV of Figure l, showing a diierent position of the circuit-breaker;

Figure 5 is a section along the line V-V of Figure l;

Figure 6 is a section along theV line Vif-VI of Figure 1,'

Figure 7 is a side view of the contact disc provided on the contact bridge with a contact stirrup;

Figure 8 shows the same disc ith stirrup seen from above;

Figure 9 shows the side guiding projection of the contactl bridge, seen from above;

Figure 10 is a form of construction of the circuitbreaker with a single spring contact and for the indirect heating of the bi-metal strip;

Figure 11 shows the circuit-breaker with another form yof construction of the spring contact and for direct heating of the bi-metal strip;

Figure 12 shows an over-current circuit-breaker with a different guide of the contact bridge;

Figure 1,3 shows the same with safety means for the guiding rod against undesirable closure of the circuit;

Figure 14 is a` perspective view of a form of construction of the circuit-breaker according to the invention especially suitable for motor vehicles with a casing mounted thereon.

On the raisedV parts l' of the base plate 2 of insulating material which is provided with bored extension anges 3 for the mounting of the circuit-breaker by means of screws, there are mounted the contact terminais 4, which are 'connected to the contact screws 6 through the connectors 5. 'The' contact screws 6 serve, on the one hand, for securing the connectors 5 and the insulating member '7' to thefbase plate 2. On the other hand, one of the two contact screws` 6 secures the bi-metal strip 8 and the other one-holds the twocontact springs 9. The bi-metal strip V8` is provided at' the end of itsk straight part with a contact 19; whichimth'e conditionA shown in Figure 1, which illustrates the interruption of the current by the circuit breaker, abuts against an inclined and insulated part of the contact bridge 11. The latter is moved by the guiding rod 12 which carries at its upper end the switch-on button 13. The guiding rod 12 and the switch-on button 13 have a tendency to move upwards owing to the action of the spring 14. In Figure l they have reached their upper limit position. In order to prevent tilting of the contact bridge 11, the latter is provided, in addition to the guide rod 12, with a lateral guide consisting of an attachment 15 which slides up and down along the longitudinally slotted rail 16 during the movement of the contact bridge. The rail 16 lies with its lower end on the insulating member 7 and is secured at its upper end t-o the metal frame 17, the side walls of which are screwed on to the insulating member 7 at their lower ends. Over the frame 17 there is mounted a casing 18 which lies at its bottom on the base plate 2 and is connected at the top to the frame 17 by means of screws 40. When the switch-on button is pressed down, the contact bridge 11, with its contact disc 19, comes to lie under the projection of the contact 10 of the bi-metal strip 8, so that a conducting connection is elected at this point between the bi-metal strip and the contact disc 19. The contact disc 19 -is continued by an angular stirrup 20 with which it is integral and which, during the downward movement of the contact bridge 11, is engaged by the springs 9. The circuit is thereby iclosed between the two terminals 4 and 6 over the bi-metal strip 8, its Contact 10, the contact disc 19, the stirrup 20 and the springs 9. When the button 13 is depressed the bi-metal strip 8 with its contact 10 is deflected laterally by its contact 10 sliding along the insulating inclined surface of the contact bridge 11 until the projection of the contact 1d engages over the contact plate 19.

In order to switch olf the circuit-breaker by hand, use is made of a button 21 which is pressed upwards by a spring 23 lying over its guiding rod 22. At the lower end of the guiding rod 22 there lies a spherical slide member 24, which abuts against the bent part 25 of the bi-metal strip. It the button 21 is depressed against the action of the spring 23, the bi-metal strip 8 moves away from the contact bridge owing to the movement of the spherical slide member 24 on its bent end 25. In this case the projection of the contact 10, which, otherwise locks the contact disc 19 against an upwards movement, is pressed away laterally so that the locking of the contact bridge 11 is removed and the same moves upwards in the position shown in Figure 1, with the result that the current is interrupted.

ln the form of construction shown in Figure l0, the Contact stirrup 20 is angularly bent at its lower end so that an inclination 26 is produced. The latter lies on a similarly angularly bent bi-metal spring 27 when a current flows through the circuit breaker. The bi-metal strip is so arranged that its angularly bent part rises during the passage of the current, thereby exerting an increased pressure on the contact stirrup 20, 26. This pressure is also transmitted to the contact bridge 11 so that an increased contact exists also in the same between the contat-ct disc 19 and the bi-metal strip contact 10 until the current is switched oit. The bi-metal strip 8 is indirectly heated by the heating element 28, in the case of Figure 10. This arrangement is suitable, more particularly in the case of circuit-breakers intended for small currents to be switched off.

The circuit-breaker illustrated in Figure ll differs from that shown in Figure 10 only by a different construction Vof the spring 27, which in this case does not consist of a metal strip and is bent differently, and by the right-angle bending of the end part 26 of the contact stlrrup as well as by the absence of any indirect heating of the bl-metal strip 8.

A very simple construction of the c1rcu1t-breaker1s shown in Figure l2, which can, for instance, be used 1nstead of the safety devices employed in automatic telephone installations, wherein, instead of the contact bridge,

only a simple contact disc 29 is provided, which is secured on the guiding rod 30, used at the same time for the conduction of the current. This rod is guided in openings provided in the insulating parts 31, 32. The walls 33, 34 of the circuit-breaker are made of metal. The fixing of the metal wall 33 over the metal wall 34 is etected in this example of construction by indentation at the point 38. The guiding rod 30 is insulated with respect to the metal wall 34 by the insulating member 35. A spring 36 rests on the insulating member 35, which spring abuts against the disc 39 provided on the guiding rod 30, and tends to move the latter upwards. The supply of the current is etected through the guiding rod 30 on the one hand, and, on the other hand, through the bayonet-like fixing of the circuit-breaker by the part 34. The bi-metal strip 8 is again provided with an indirect heating element 24 which elects the displacement of the contact 10 away from the disc 29 and thereby the interruption of the current.

The circuit-breaker illustrated in part view in Figure 13 differs from that shown in Figure l2 in that the guiding rod 30 is provided underneath the contact disc 29 with an insulating sleeve 37 in order that after the switching-ott, when the bi-metal strip returns into its original position, an undesirable renewed circuit closure between the contact 10 and the guiding rod 30 is prevented. The passage of the current is reinstated only when the guiding rod is depressed and the contact 10 has again assumed its position over the contact plate 29.

Figure 14 illustrates an arrangement which facilitates the removal and replacement of the circuit-breakers. Thus, the same is provided with slotted metallic plug-in pins 45 whose prongs are spread apart as indicated at 46. The breaker is housed in an insulating casing 52 which has laterally extending insulating cover parts 53 and 54 recessed as at 55 to receive and cover the binding posts of a base which receives one or several of the circuit-breakers with their terminals 45 permitting ready removal of the same. Thus, the binding posts on the base are protectively covered by the portions 53 and 54 when the circuits are in use.

I claim:

l. A thermal over-current circuit breaker comprising an insulating base member, an insulated contact bridge mounted to move toward and away from said base member, and having an insulating side wall with an inclined portion, a spring urging said contact bridge away from said base member to a circuit-open position, a contact disc on said contact bridge having a conductive part connected thereto and projecting from said bridge toward said base member, a bimetallic strip secured at one end to said base member and a Contact piece secured near its other end, said piece being shaped to engage said disc and to latch said bridge in its circuit-closed position against the force of said spring whenever said strip is undeilected, the inclined portion of the side wall being arranged to move the bimetallic strip aside during movement of the bridge to circuit-closing position and allowing the strip to snap back and latch the bridge when the latter has reached its circuit closing position; and two conductive connection elements on said base member, one connected to the secured end of said bimetallic strip and the other disposed for engagement by said conductive part projecting from the bridge member when the bridge is in its circuit-closed position.

2. A thermal over-current circuit breaker comprising an insulating base member, an insulated contact bridge mounted to move toward and away from said base member, and having an insulating side wall, a spring urging said contact bridge away from said base member to a circuit-open position, a Contact disc on said contact bridge having a conductive part connected thereto and projecting from said bridge toward said base member, a bimetallic strip secured at one end to said base member and a contact piece secured near its other end, said piece being shaped to'engage said disc and to latch said bridge in its circuit-closed position against the force of said spring whenever said strip is undeected, two conductive connection elements on said base member, one connected to the secured end of said birnetallic strip and the other comprising a contact spring disposed for engagement by said conductive part projecting, from the bridge member when the bridge is in its circuit-closed position; and two plug pins outside said base member connected respectively -to said two elements. Y

3. A circuit breaker according to claim 2, in which said plug pins are slitted and have each an enlargement on their free ends for engagement behind the back face of the sleeves holding the circuit breaker on the terminal block.

4. A circuit breaker in accordance with claim 2, in which said contact spring vis formed of bimetal material.

5. A circuit breaker in accordance with claim 2, in which said contact spring has its ends bent toward one another to receive therebetween the conductive parts projecting from the bridge.

6. A thermal over-current circuit breaker comprising an insulating base member, an insulated contact bridge mounted to move toward and away from said' base member, and having an insulating side wall, a spring urging said Contact bridge away from said base member to a` circuit-open'position, a contact disc on said contact bridge having a conductive part connected thereto and projecting from said bridge toward said base member, a bimetallic strip secured at one end to saidV base member and a contact piece secured near its other end, said piece being shaped to engage said disc and to latch said bridge in its circuit-closed position against the force of said spring Whenever said strip is undeflected, and two conductive connection elements on said base member, one connected to the secured end of said bimetallic strip and the other disposed for engagement by said conductive part projecting from the bridge member when the bridge is in its circuit-closed position; the free end or" said bimetallic strip being bent away from said contact bridge, and button means for engaging said bent portion to deect the bimetallic strip ont of latching engagement with said bridge.

7. A circuit breaker in accordance with claim 6, in which said button means comprises a guide stem and a ball end for engaging the bent portion of said bimetailic strip.

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